1. Field of the Invention
The present invention relates to a method for manufacturing a semiconductor device which has a circuit including a thin film transistor (hereinafter, referred to as a TFT) in which a channel formation region is formed using an oxide semiconductor film. For example, the present invention relates to a method for manufacturing a semiconductor device which is mounted on an electro-optical device typified by a liquid crystal display panel or a light-emitting display device including an organic light-emitting element.
Note that the semiconductor device in this specification indicates all the devices which can operate by using semiconductor characteristics, and an electro-optical device, a semiconductor circuit, and an electronic appliance are all included in the semiconductor devices.
2. Description of the Related Art
In recent years, active-matrix display devices (such as liquid crystal display devices, light-emitting display devices, or electrophoretic display devices) in which a switching element of a thin film transistor (TFT) is provided for each of display pixels arranged in matrix have been actively developed. In the active-matrix display devices, a switching element is provided for each of pixels (or each of dots), and thus, there is such an advantage that the active matrix display devices can be driven at lower voltage than passive matrix display devices in the case where the pixel density is increased.
In addition, a technique has attracted attention, where a thin film transistor (TFT) or the like in which a channel formation region is formed using an oxide semiconductor film is applied to electronic devices or optical devices. For example, a TFT in which ZnO is used for an oxide semiconductor film or a TFT in which InGaO3(ZnO)m is used for an oxide semiconductor film can be given. A technique in which a TFT including such an oxide semiconductor film is formed over a light-transmitting substrate and used as a switching element or the like of an image display device is disclosed in Patent Document 1 and Patent Document 2.